1. Field of the Invention
This invention relates to electrochromic devices which are useful as transmission-type devices such as smart windows, reflection-type devices such as antiglare mirrors for automobiles and decorative mirrors, and displays.
2. Description of Related Art
A method of forming a chromogenic layer for an electrochromic device hereinafter referred to as an EC device such as smart windows is known from Japanese Laid-Open Patent Publication No. 63-18336 disclosing a method in which a film of chromogenic layer is formed by vacuum-evaporating an electrochromic active substance such as tungsten oxide (WO3) over a transparent electrically conductive film.
However, this method requires techniques carried out under vacuum conditions, which lead to elevated production costs and the requirement of a large-sized vacuum apparatus for the production of an EC device with a large-surface area.
There have been reported various EC devices containing an organic electrochromic compound such as viologen derivatives in the ion conductive layer as disclosed in Japanese Patent Laid-Open Publication Nos. 9-120088 and 7-702118. However, these EC devices have large leakage current and must be electrified all the time to maintain the coloration state. Furthermore, a long time coloration causes a problem that remnant coloration occurs even after decoloration. The present invention was made in view of such situations and intended to provide an EC device which is less in leakage current and can reduce the remnant coloration caused by long time coloration.
After extensive research and study for solving the foregoing problems, it was found that the problems could be solved with an EC device having an ion conductive layer containing an electrochromic polymer as described below.
That is, the EC device according to the present invention wherein an ion conductive layer is provided between a pair of electrically conductive substrates at least one of which is transparent is characterized in that the ion conductive layer contains an electrochromic polymer which is a reaction product of a polymer having reactive groups with the following organic compound.
The organic compound is an organic compound having both a structure exhibiting cathodic electrochromic properties and a structure exhibiting anodic electrochromic properties and further functional groups reactive with the reactive groups of the polymer.